JP2002322316A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an acrylonitrile-butadiene rubber composition having oil resistance and heat resistance and excellent in properties easily removed from metals without remaining residues. SOLUTION: The acrylonitrile-butadiene rubber is mixed with (a) an amide compound having a melting point of 100 deg.C or higher, (b) a phosphorus compound having a pH of less than 7, and (c) a phosphite compound. This formulation results in the rubber composition having oil resistance and heat resistance and excellent in properties easily removed from metals without remaining residues.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an acrylonitrile butadiene rubber composition. More specifically, the present invention relates to an acrylonitrile butadiene rubber composition having excellent oil resistance and heat resistance and not sticking to a metal at a portion used in contact with the metal.

[0002]

2. Description of the Related Art Acrylonitrile butadiene rubber is a material having both oil resistance and heat resistance, and is widely used as rubber parts such as diaphragms, packings, gaskets, O-rings, hoses, needle valves, etc. in areas that come into contact with oil. I have. Many of these rubber parts are replaced as needed or periodically due to factors such as inspection and aging. When these rubber parts are to be collected, the rubber sticks to the metal side, making it difficult to peel off the rubber, which sometimes hinders the part replacement work.
In addition, if parts are mounted with a part of the rubber remaining on the metal, sufficient sealing performance cannot be exhibited, which may be a major cause of serious defects such as malfunction, oil leakage, foreign matter inclusion, etc. There is. In particular, in a portion that comes into contact with oil, a phenomenon in which rubber and metal adhere to each other is conspicuous.

[0003] In order to solve such a problem, it is known, for example, in Japanese Patent Application Laid-Open No. Hei 6-88005 to incorporate a phosphate ester plasticizer. Also, for example, in Japanese Patent Application Laid-Open No. 10-298350, there is a method of blending acrylonitrile butadiene rubber with an ethylene rubber.

[0004] As the performance of the engine has been improved, these parts have been required to have higher performance at high temperatures, and the requirement for metal adhesion resistance has become more severe. Among them, the above technique does not provide satisfactory metal fixation resistance. Further, there is a method in which a portion of the rubber component that comes into contact with a metal is coated with silicone, a fluorine-based resin, or the like, or a graphite or molybdenum compound is applied.

[0005]

However, in these methods, there is a possibility that the surface treatment agent may be mixed in as a foreign substance, and the number of steps for performing the surface treatment increases, which is disadvantageous in cost.
There is also a method in which only the surface layer is cured or made into a resin by a chemical modification method. However, there is a problem in that the sealing property is reduced, oil leaks, and operation failure occurs.

[0006]

Means for Solving the Problems As a result of intensive studies, the authors found that acrylonitrile-butadiene rubber (a) at 100 ° C.
A rubber composition having oil resistance and heat resistance and excellent metal adhesion resistance by blending an amide compound having the above melting point, (b) a phosphorus compound having a pH of less than 7, and (c) a phosphite compound. They found something and completed the present invention based on this finding. Thus, according to the present invention, there is provided an acrylonitrile-butadiene rubber composition having oil resistance and heat resistance and having excellent metal adhesion resistance.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Acrylonitrile butadiene rubber used in the present invention is a copolymer of acrylonitrile and butadiene, and there are many grades depending on the polymerization ratio of monomers, Mooney viscosity of the polymer, and the like. Low Mooney viscosity polymers contain more low molecular weight components and are therefore highly tacky, which is disadvantageous for metal adhesion resistance. Therefore, a polymer having a Mooney viscosity of 70 or more is desirable from the viewpoint of metal adhesion resistance. The amide compound having a melting point of 100 ° C. or more used in the present invention is represented by Chemical Formula 1. In Formula 1, R ¹ and R ² each represent an alkyl group or an aryl group, and n represents an integer of 1 or more. Specific examples include methylene bisstearamide, ethylenebisstearamide, ethylenebisoleylamide, butylene bisstearamide, and ethylenebisphenylamide. These may be used alone or in combination. The amount added is generally 0.1 to 15 parts by weight, preferably 1 to 10 parts by weight, per 100 parts of rubber.

[0008]

Embedded image The phosphorus compound having a pH of less than 7 used in the present invention is shown in Chemical formula 2. R ^{3 in} Chemical Formula 2 is composed of an alkyl group, an aryl group, an alkoxypolyalkylene ether group, or a phenoxypolyalkylene ether group, and fluorine may be contained in the constituent elements. m is an integer of 1-2, n is an integer of 1-2, and m + n = 3. R ³ when m = 2 may be different from each other. Specifically, monododecylphosphonic acid, didodecylphosphonic acid, mono (ethoxytriethyleneglycol) phosphonic acid, di (ethoxytriethyleneglycol) phosphonic acid monophenylphosphonic acid,
Examples include diphenylphosphonic acid, ditolylphosphonic acid, and monononylphenylphosphonic acid. These may be used alone or in combination of two or more. The amount of addition is generally 0.1 to 15 parts by weight, preferably 1 to 10 parts by weight, per 100 parts of rubber.

[0009]

Embedded image

The phosphite compound used in the present invention is represented by the following chemical formula (3). R ⁴ , R ⁵ , and R ^{6 in} Chemical Formula 3 are each composed of an alkyl group, an aryl group, an alkoxypolyalkylene ether group, or a phenoxypolyalkylene ether group, and the constituent elements may contain fluorine. Specifically, triphenyl phosphite, diphenyl decyl phosphite, diphenyl monooctyl phosphite, monophenyl dioctyl phosphite, trinonyl phenyl phosphite, triphosphite (trit -Butylphenyl) ester, 1,3-phenylene-bisdiphenylphosphite, 1,3-phenylene-bisdixylenylphosphite, 2,2-methylenebis (4,6-di-tert-butylphenyldioctylphosphite), 4,4'-isopropylidenebis (phenyl dilauryl phosphite), 4,4'-butylidenebis (3-methyl-6-t-butylphenyl-
Di-tridecyl phosphite). These may be used alone or in combination of two or more.
The amount added is generally 0.1 to 15 parts by weight, preferably 1 to 10 parts by weight, per 100 parts of rubber.

[0011]

Embedded image The vulcanizing agent is not particularly limited, and a vulcanizing agent generally used for acrylonitrile butadiene rubber may be used. For example, sulfur / vulcanization accelerator systems, peroxide / co-crosslinker systems. In the rubber composition obtained in the present invention, a compounding agent usually used for rubber can be arbitrarily compounded. For example, fillers used in the present invention include carbon black, silica, clay, talc, calcium carbonate, diatomaceous earth, quartz powder and the like. Further, a plasticizer, a processing aid, a lubricant, an antioxidant, a pigment, a silane coupling agent, and the like can be arbitrarily compounded. The method for preparing the rubber composition of the present invention is not particularly limited, and the rubber composition can be prepared by adding the above-mentioned components and mixing with a conventional kneading machine such as a Banbury mixer, a kneader or a roll. The rubber composition thus obtained can be vulcanized at a temperature of about 150 to 200 ° C. for about 2 to 20 minutes. Secondary vulcanization may be performed if necessary.

[0012]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples. Parts are by weight unless otherwise specified.
Press vulcanization was performed at 170 ° C. for 10 minutes to obtain a test piece. The evaluation of the metal fixation resistance was as follows. After compressing the O-ring on a steel metal plate at a compression ratio of 25%, the O-ring was immersed in a closed container filled with engine oil at 130 ° C. for 500 hours. Thereafter, the O-ring was taken out, and the presence or absence of sticking to the metal was evaluated.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

As described above, according to the present invention, an acrylonitrile-butadiene composition having excellent oil resistance and heat resistance and also having metal adhesion resistance can be provided. A part used for a part to be provided can be provided.

Claims (4)

[Claims] 1. A rubber composition characterized by blending (a) an amide compound having a melting point of 100 ° C. or more, (b) a phosphonic acid compound, and (c) a phosphite compound with acrylonitrile butadiene rubber. 2. A rubber composition, wherein the compound (a) according to claim 1 is an amide compound represented by the following chemical formula 1. Embedded image (R ¹ and R ² each represent an alkyl group or an aryl group;
n represents an integer of 1 or more. ) 3. The compound (b) according to claim 1, wherein
A rubber characterized by being a phosphonic acid compound represented by
Composition. Embedded image (R³Is an alkyl group, an aryl group, an alkoxypolyal
Chelen ether group, phenoxy polyalkylene ether
Even if the constituent elements contain fluorine
Good. m is an integer of 1-2, n is an integer of 1-2, and m + n
= 3. R when m = 2³Are different
May be. ) 4. A rubber composition, wherein the compound (c) according to claim 1 is a phosphite compound represented by the following chemical formula (3). Embedded image (R ⁴ , R ⁵ , and R ⁶ are each composed of an alkyl group, an aryl group, an alkoxypolyalkylene ether group, or a phenoxypolyalkylene ether group, and the constituent elements may contain fluorine.)